This invention relates generally to systems for cooling electric machines and, more particularly, to a cooling jacket for cooling an electric motor and/or generator having high heat-dissipation requirements.
This invention is in the same field as U.S. Pat. No. 6,300,693, entitled xe2x80x9cElectric Motor Cooling Jacket Assembly and Method of Manufacturexe2x80x9d, assigned to Emerson Electric Co., which is incorporated by reference herein for all purposes. The ""693 patent discloses a cooling jacket having axial passages for the flow of coolant to cool the stator of an electric machine (a motor or generator), such as a brushless permanent magnet motor operating at high speeds and driven by fuel-powered turbines to generate electrical power. While the cooling jacket design described in the patent is generally satisfactory, the flow passage configuration used in the design is not optimal from the standpoint of cost and heat transfer efficiency.
Among the several objectives of this invention is the provision of an improved cooling jacket for an electric machine (e.g., motor and/or generator); the provision of such a jacket which comprises an assembly of parts which are relatively economical to manufacture and easy to assemble; the provision of such a jacket which is adapted for the efficient cooling of an electric machine having high heat dissipation requirements; and the provision of such a jacket having coolant flow passages which are designed to minimize the quantity of materials used while maximizing heat transfer efficiency.
In general, a cooling jacket of the present invention is used for cooling the stator of an electric machine. The jacket comprises a jacket body having co-axial inner and outer surfaces defining a generally cylindric cavity for receiving the stator so that the stator is in heat transfer contact with the inner surface. The body has axial flow passages for the flow of coolant therethrough, each flow passage having a radial cross sectional shape defined entirely by three or more substantially linear sides. A first end cap is connected to one end of the cooling jacket body and defines an annular conduit around the body in fluid communication with the flow passages. A second end cap is connected to the opposite end of the cooling jacket body and defines an annular conduit around the body in fluid communication with the flow passages. An inlet is provided on one or the other of the end caps for flow of coolant into a respective conduit, and an outlet is provided on one or the other of the end caps for flow of coolant out of a respective conduit. Barriers in the conduits direct fluid along a path from the inlet through the flow passages to the outlet.
In another aspect of the invention, the axial flow passages in the body have a radial cross sectional rectangular shape defined by four substantially linear sides. The substantially linear sides are joined at four corners, each corner having a small radius of curvature such that the perimeter of the flow passage is not reduced by more than 25% compared to the same flow passage having square corners. The barriers in the conduits direct the coolant along a single serpentine path from the inlet through the flow passages to the outlet.
In another aspect of the invention, the flow path comprises a plurality of parallel flow sections extending axially of the cooling jacket body between the conduits. Each flow section of the path comprises a group of flow passages and each section has an inlet end for entry of coolant into a respective group of flow passages and an outlet end for exit of coolant from the flow passages. Ramps in the conduits extend across the inlet and outlet ends of the parallel flow sections for maintaining a substantially uniform static pressure in the conduits across the flow passages of each section.
In another aspect of the invention, the barriers direct all fluid entering the inlet to flow through the flow passages along only one serpentine path starting at the inlet and ending at the outlet and extending around substantially the entire circumference of the jacket body.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.